The present invention generally relates to three-dimensional measuring methods and systems, and more particularly to a three-dimensional measuring method which makes a three-dimensional measurement based on an image which is picked and/or imaged up by a camera or the like and to a three-dimensional measuring system which employs such a three-dimensional measuring method.
It is particularly important in the field of factory automation that a measurement of three-dimensional information including depth information can be made by a robot or the like. This function is essential to proper operation of a robot eye when moving a robot arm of a robotic device to proper operation of a desired position, for example.
Conventionally, there are the following three methods (1)-(3) of making the three-dimensional measurement using a camera.
(1) A first method picks up the image by a range sensor which uses the fact that the reflection time of the ultrasonic wave becomes different depending on the distance. PA1 (2) A second method picks up the image by two or more cameras, and uses the fact that the parallax becomes different between the picked up images depending on the distance. PA1 (3) A third method picks up a moving image by an ordinary camera. For example, the moving image is made up of a predetermined number of still images which are picked up per second. A change between the two still images which are mutually time-adjacent, and the three-dimensional information are calculated based on the change.
The first method (1) is simple in that the depth information can be obtained directly. However, special equipment is required.
The second method (2) requires the positional relationship of the two or more cameras to be fixed. For this reason, it is difficult and troublesome to adjust the positions of the cameras.
The third method (3) calculates the three-dimensional information based on the assumption that only one body exists in the picked up image, that the brightness at each point on the body does not change with time, that and the brightness spatially changes smoothly. Based on these assumptions, the quantities which are to change between time-adjacent images are calculated by making the manner of the movement and the depth at each point on the image unknowns. Then, equations are solved by setting the calculated quantities equal to the observed changes, so as to calculate the manner of a body is movement and the depth at each point on the image.
This third method (3) has advantages in that the processing can be made using a single camera and that no difficult and troublesome adjustments are required in advance. However, the third method (3) can only be applied for the case where the image contains only one body (or object). In addition, because the information which is used relates to the moving image, there is a problem in that the accuracy of calculated three-dimensional information is not very good.